Answer :

When we inhale and exhale a process known as breathing takes place. During breathing ; gaseous exchange , that is ; excretion of carbon dioxide and inhalation of oxygen takes place.

Remark : - Dont confuse respiration and breathing. They are different processes. Breathing simply means inhalation of oxygen and exhalation of carbon dioxide ; while respiration means  involves breakdown of food and it is a deeper process.
A process called breathing takes place when we inhale oxygen and exhale carbon dioxide .